People spend hours at a time with their electronic devices—computers, mobile phones, music players, and the like. They like best those devices that are intuitive to use and whose interactions best meet their expectations regarding how machines should work. They interact with electronics through inputs and outputs from the devices, where the outputs generally are provided audibly and/or on a flat graphical display screen, and the inputs may occur via touchscreens, joysticks, mice, 4-directional keypads, and other such input mechanisms. As mobile devices become more powerful, users interact with them more using graphical objects, such as lists of items, maps, images, and the like.
Moreover, users have come to expect more rapid and intuitive user interfaces for such mobile devices. This has lead to developments in the area of gestures-based interaction with computing devices, such as through the use of two dimensional (2D) trajectories drawn by users with their finger on a touchscreen or with a pen. These gesture-based user interfaces typically employ gesture recognition software, which can include template-based recognizers or parametric-based recognizers.